Spark gap device having insulators in the form of plasters



U. DIBBERN June 17, 1969 SPARK GAP DEVICE HAVING INSULATORS IN THE FORM OF PLASTERS Filed June 20, 1967 INVENTOR.

U WE DI BB ERN AGEN United States Patent 3,450,929 SPARK GAP DEVICE HAVING INSULATORS IN v THE FORM OF PLASTERS Uwe Dibbern, Hamburg, Germany, assignor, by mesue assignments, to US. Philips Corporation, New York, N.Y., a corporation of Delaware Filed June 20, 1967, Ser. No. 651,935 Claims priority, application Germany, June 24, 1966,

.P Int. Cl. H01j 1/00; H01t 1/00 U.S. Cl. 313-325 Claims ABSTRACT OF THE DISCLOSURE The invention relates to spark gap devices having surface-guided spark gaps on insulators arranged between the electrodes.

Spark gap devices in the form of surface-guided spark gaps as used in data processing for printing and punching have a limitation in that the insulators are eroded away by burning.

In order to obviate this disadvantage it has been proposed to use either a solid insulator which is movable and is fed forward as it is consumed or a liquid along the surface of which the spark is produced.

In contrast therewith the invention is characterized in that the insulator is a spark gap device having a surfaceguided spark gap on an insulator arranged between the electrodes, characterized in that the insulator is a movably arranged paste capable of replenishing the consumed part by such movement. From a constructional point of view, replenishing a paste, like that of a liquid, is simpler than feeding forward a solid insulator. On the other hand, the surface of a paste like that of a solid may be arranged in any desirable position, whereas the surface of a liquid must always be kept horizontal.

A further advantage of a paste as compared with a liquid is that it is simpler to prevent a paste from being dispersed by the sparks.

In order that the invention may readily be carried into effect, an embodiment thereof will now be described with reference to the accompanying diagrammatic drawing, the single figure of which is a sectional view of an embodiment of a spark gap device using an insulator in the form of a paste.

Referring now to the figure, a block 4 of insulating material is provided at its front face with two electrodes 1 and 2 of a sparking circuit. An electrode 3, which may however be dispensed with, acts as an ignition electrode. A supply of paste is contained in a cavity 4 which takes the form of a cylindrical bore in the insulating block 4. The cavity 4' is closed at one end by a piston 6. The piston is arranged to be displaced by means of a screW-and-thread drive 6' so as to feed forward fresh paste. Feeding may be effected, for example, by a small electric motor the rotation of which can be simply controlled in accordance with the number of sparks. As an alternative, it may be controlled by an operating-time counter. The sparking circuit may have any known suitable design.

A suitable paste is a colloidal mixture of a finely powdered insulator, for example A1 0 and a liquid. Precipitation of the grains may be prevented by making the mixture thixotropic, for example, by the addition of finely powdered SiO (available under the trade name Aerosil). Alternatively a paste may be used which consists only of a liquid and finely dispersed SiO A suitable liquid is, for example, water. In many arrangements the resulting conductivity is so small as to be harmless. Water has the following advantages: it is cheap and incombustible, it vaporises without a residue and, as it is an inorganic liquid, no carbon is produced on its decomposition by the sparks. Drying of the paste may be prevented by the addition of a hygroscopic substance, for example AlCl A paste having better insulating properties may be made by the use of another liquid, for example transformer oil, glycerine, silicone oil or a fluorocarbon.

When using such pastes the replenishment need not exactly match the consumption, on the contrary, preferably it slightly exceeds consumption so that there always is a sufficient amount of insulating material. In the case of an excess of paste the consumption increases and an equilibrium will be established. However, even a larger excess is not critical. In punching or printing operations some of the excess paste may be transferred to the paper, however, since this will be a minute amount on a large area of paper no harm will be done.

What is claimed is:

1. In a surface-guided spark gap device, an insulating support having a cavity disposed in one surface of the insulating support, two spaced spark electrodes arranged on the surface of the insulating support overlying the cavity, a consumable insulating paste disposed within the cavity between the two spark electrodes, and means for replenishing the consumed portion of the insulating paste.

2. A spark gap device as claimed in claim 1, characterized in that the paste is a colloidal mixture of a finely powdered insulating material, for example A1 0 and a liquid.

3. A spark gap device as claimed in claim 1, characterized in that the paste comprises finely powdered SiO 4. A spark gap device as claimed in claim 1, characterized in that the paste consists of a liquid containing finely dispersed SiO 5. A spark gap device as claimed in claim 1, characterized in that the liquid constituent of the paste is water.

6. A spark gap device as claimed in claim 1, characterized in that a hygroscopic substance, is added to the paste.

7. A spark gap device as claimed in claim 2, characterized in that the liquid constituent of the paste is transformer oil.

8. A spark gap device as claimed in claim 2, characterized in that the liquid constituent of the paste is glycerine.

9. A spark gap device as claimed in claim 2, characterized in that the liquid constituent of the paste is silicone oil.

10. A spark gap device as claimed in claim 2, characterized in that the liquid constituent of the paste is a fluorocarbon.

References Cited UNITED STATES PATENTS 2,657,248 10/1953 Smits 313-131 X 3,196,041 7/1965 McNulty et al. 313-131 X JOHN W. HUCKERT, Primary Examiner. R. F. POLISSACK, Assistant Examiner.

US. Cl. X.R. 

